I don't know which MES you have the 30" or 40"? I have the 40", what has already been said is accurate, if using chips, I put in about 1/3 cup, its not a lot. I soak my chips others here don't agree, but honestly, they start right up within a 2 or 3 minutes. Again talking chips here, some bags of chips have a vast assortment of chips sizes, so I use a strainer, this gets a very even size of chips and more consistent results in burn time and smoke.
Again I only get about 1/3 cup no more than 1/2 cup. That is to start, and the smoke is initially white but settles in about 15 minutes to TBS. If only chips I add chips about every 30-45 minutes. If you want more smoke but don't want to have the bitter over smoked tastes, you can go with 1/2 cup but when you put the chips in the tray, make sure they are evenly distributed so when you rotate the chip tray, it dumps the not in one pile but fairly evenly in the burner tray. This isn't exact you have to play with it to find out the max your smoker/burner tray can effectively keep going.
I mainly use chips and chunks. My first 15-20 minutes is with chips only, then I add 2 or 3 (1 x 1 x 1 chunks) if you use 3 chunks evenly distribute across the tray. If you are using uneven chunks remove the tray and use tongs to drop the chunks in then replace the tray, making sure it rotates and moves freely. When the smoke starts to die off I then put a few chips and 2 chunks. Time will depend on how efficient of burn you are getting.
Do you always clean the burning tray? Take a wire brush or BBQ wire brush and brush out all the buildup, down to the metal. This will help the chips burn better. Ok here is one last tip and some may agree or may not. I do a minimum preheat to 270 deg 1 hour in the summer had 2+ hours in the winter. The primary reason is so all the metal mass will be thoroughly heated and when you add meat, recovery is much faster and the MES will hold temp better during the smoking process. But a by-product is the burning tray will be very hot, try to make sure the element is on when you add the first wood chips/chunks after you have loaded your meat, there should be no problem with ignition.